Cochise County Insects: Brachinus Bombardier Beetles


Aha! I knew not…but now realize I’d found a broup of Brachinus bombardier beetles. They turned up in southern Cochise County, Arizona, in the early spring of 2012. The exact species is hard to pin down without a microscope, so we won’t go there, but what a find nonetheless!

When I shifted a window air conditioner in one of our storage sheds, eight or ten little beetles began scrambling for cover. Sort of, that is. Not only did I need help with insect identification, but I felt sorry for the little guys (or gals).

They were clearly confused by the sudden exposure to sunlight, and no wonder. While the wing-area carapace looked normal enough–a dark, glossy surface with an irridescent green tint–the thorax and head were naked. I’d be confused, too, if I had to face the world dressed like that.

That’s the way they looked, anyway, like they were missing the forward halves of their otherwise normal exoskeletons.

Kind of gross, but also kind of fascinating.

Activity: When they were “uncovered”, they were clearly distressed…but also had no idea which way to go. There were other things in the shed under which they could have crawled. Instead, they went in “lost circles” wondering why the Great Bug God had uncovered their sure-thing shelter.


The photos are larger than life size by a fair margin; the actual beetles couldn’t be more than 1/4″ long at most.



Once they were identified as bombardier beetles, the fact that I’d not disturbed them by trying to capture one (which I would never do because it would be just plain rude) turned out to be a good thing. They have chemicals that “bomb away” in their own defense. Get this quote from an article titled The Amazing Bombardier Beetle at

…Dr Schildknecht discovered that in the beetle’s specially designed combustion tubes are two enzymes called catalase and peroxidase which make chemical reactions go millions of times faster. These chemicals catalyze the extremely rapid decomposition of hydrogen peroxide into water and oxygen and the oxidation of hydroquinone into quinone, causing them to violently react and explode—but not so soon as to blow up the beetle, of course!

The beetles were comfortably “resting” on a bare, raw-plywood floor under a metal air conditioner, but there was no indication they considered anything in the area to be a food source. Some online sources say the bombardiers do tend to congregate in groups between hunting forays, so that makes sense. They didn’t seem to be chewing the wood or, for that matter, the wiring in the AC unit.

They were just…there.



Fascinating. Fascinating. Fascinating. I’d heard the term somewhere but had no real idea what it meant to be a bombardier beetle. We had a guy in the Army who could pass gas on command–he once won a bet by lying butt-up on his top bunk and blasting away 60 times in 3 minutes–but his emissions weren’t particularly deadly.

Not that I got close enough to make that determination, but several other soldiers did, one with a watch to make sure that Albert (that was the gas man’s name) performed in full before collecting his winnings.

No, these Brachinus bombardier beetles go far beyond that. Sophisticated chemical warfare, firepower beyond compare.

What a bug, eh?




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